Electron emitting device



Sept- 20, 1932 w. J. ALBERSHEIM 1,878,089

ELECTRON EMITTING DEVICE Filed June 19. 1926 Patented Sept. 2G, 1932 UNITED STATES PATENT oFFlcE WALTER J'. ALBERSHEIH, 0F NEW YORK, N. Y.; ASSIGNOR TO RADIO CORPORATION OF AMERICA, 0F NEW YORK, N. Y., A CORPORATION OF DELAWARE ELECTRON EMITTING DEVICE Application led June 19, 1926. Serial No. 117,086.

This invention relates more particularly to a class of devices adapted to be used in wireless electric systems.

My invention has for its object primarily to provide a device in the form of a cathode designed to be employed in conjunction with the anodes and input electrodes of audions, amplifiers and like devices used in wireless electric or so-called radio systems for emitting electrons with voltage luotuations being largely eliminated therefrom so that the signals transmitted and amplified will be uniform and free from foreign electrical influences and noises which frequently accompany the voltage impulses and tend to interfere with and-distort the true amplification of the signals.

The invention consists essentially of the provision in an evacuated bulb having an output anode and an input electrode of a heating coil formed preferably of a single strand centrally bent and helically coiled into two closely spaced convoluted members of equal electrical resistance. The heating coil is mounted within an electron emitting cathode preferably of a capsule shape with the middle point of the coil fixed or connected to the peak of the capsule, and embracing the entire heatable space between the coil. and the cathode is an electrically insulating but heat conductive member for transmitting heat from the coil to the cathode for causing emission of electrons and for preventing the transmission of voltage fluctuations Jfrom the coil when heated to the cathode in order that the electrons will not be aiected by the voltage fluctuations.

A further object of the invention is to provide an electron emitting device of a simple and eiiicient construction which may be made in appropriate sizes and shapes.

With these and other objects in view, the invention will be hereinafter more fully described with reference to the accompanying drawing forming a part of this specification in whichsimilar characters of reference indicate corresponding parts inall the views and will then be pointed out in the claims at the end of the description.

In the drawing, Figure 1 is a diagrammatic view of one form of a wireless electric circuit employing an audion tube provided with one form of my improved electron emitting dev1ce.

Fig. 2 is an enlarged sectional view, partly in elevation, taken through the tube, and

appropriate form of audion or radio tube,

though the audion illustrated has the usual evacuated bulb 11 supported on the base 12, and in the base is the stem 13 of glass or other insulating material. The upper portion of the insulating stem 13 protrudes some distance interiorly of the tube, and projecting from the central part of the upper end of this stem is a cylindrical extension, as 14.

Extending outwardly from the base 12 are two pins 15, 16. Embedded in the stem 13 and leading from the pin 15 through the extension 14 of the stem is a conductor or lead 17. Also embedded in the stem 13 and leading from the pin 16 through the extension 14 is another conductor or lead 18. The conductors or leads 17, 18 are in spaced relation, and are of such lengths that their upper ends protrude above the extension 14 of the stem 13 into the evacuated bulb 11.

Interiorly of the evacuated bulb is a heating coil or filament 19 preferably of abifilar type formed from a single thread or strand which is centrally bent into a loop Which is helically coiled to provide two closely spaced coiled strands or sides 20, 21 which are spirally convoluted, as illustrated. The free end of the side 20 of the coiled loop is attached at 22, to the protruding end of the lead 17 of the pin 15, and the free end of the other side 21 of the coil is attached at 23 to the protruding end of the lead 18 of the pin 16. The material of the coil is of uniform thickness and the sides 20, 21 being of corresponding lengths both sides have equal electrical resistance, and the bend of the filament or juncture of the sides of the coil may be considered as a neutral point 23.

Within the evacuated bulb 11 and spaced from the heating coil 19 is a cathode sleeve 24 for emitting electrons and while the cathode sleeve may be of any appropriate vthe coating may be of thorium or barium oxide or other metal or material to intensify and facilitate electron discharges. The capsule shaped cathode sleeve is disposed coaXially over the heating coil 19 so that its Wall 25 surrounds the coil, and the cathode sleeve is of such a size that it is spaced from the eonvolutions of the coil. The `neutral point of the coil is connected, at 27, to the peak 26 of the cathode, and the wall 25 of the cathode sleeve is somewhat longer than the coil.

Between the heating coil 19 and the cathode sleeve 24 is a tubular insulator 28 of thin porcelain or other suitable material adapted to conduct heat fromv the coil to the cathode, but which is an insulator against the transmission of electricity from the coil proper to the cathode sleeve. The insulator 28 is preferably of the shape of a capsule similar to the form of the cathode sleeve 24 to provide an annular wall 29 and a top or peak 30, and is preferably of such a size that-it contacts with the inner surface of the cathode sleeve. The wall 29 of the insulator 28 is of such a diameter and length that the lower end of the wall is fitted on the cylindrical extension 14 of theV insulating stem 13 of the base 12 of the audion. The neutral point 23 of the heating coil 19 extends through a hole 31 in the peak 30 of the insulating capsule 28, and in the lower part of the wall of this insulator is a vent 32, from the interior of the insulator. The insulator 28 thus embraces the entire heatable space between the coil 19 and the cathode sleeve 24 so that the coil when electrically heated, as will be later explained, will cause 'discharges of electrons from the cathode sleeve.

Within the bulb 11 of the audion is an anode or output electrode 33 which may be of any appropriate type, lthough the anode shown is in the form of an annular plate 34 which surrounds the cathode 10, and this anode or output plate is of such a diameter 'that it is spaced quite a distance from the cathode sleeye 24. Part of the anode 33 is supported dn the upper end of a conductor or lead 35 having its lower portion embedded in the insulating stem 13, and this conductor leads to a pin 36 which protrudes from the base 12 in spaced relation to the pins 15, 16 of the heating coil 19. The opposite part of the anode 33 is supported on the upper end of a support rod or wire 37 having its lower portion embedded and terminating in the insulating stem 13.

Interiorly of the bulb 11 and in the space grid lead 39 is embedded in the insulating stem 13 and leads to a pin 41 projecting from the base 12 of the bulb 11 of the audion in spaced relation to the pins 15, 16, 3G. The `grid support 40 disposed about midway between the lead 35 of the anode 33 and the cathode 10, and the lower end of this grid support 40 is embedded and terminates in the upper part of the insulatingT stem i3. ()n the lead 39 and on the support 40 is helically wound the grid wire 42 so that the convolutions of the grid are spaced from each other, and this grid as well as the anode may be approximately similar in length tothe length of the convolu'ions of the heating coil 19.

In practice the audion thus formed may be used in any suitable wireless or radidelectrie circuit, as 43. '1" he circuit has a conductor 44 leading from the antenna 45 to the primary winding or coil 46 of an input transformer 47, and a conductor 48 leads from the primary winding of the transformer to ground 49. Associated with the secondary winding or coil 50 of the transformer 47 is a Vari able condenser 51, and connected to one end of the secondary coil of the input transformer is a conductor 52 which leads to the input electrode or grid 38. To the other end of the secondary coil of the transformer 47 is connected a conductor 53 which leads to a potentiometer 54 and to a conductor 55 leading from one terminal of a battery, as B. The filament or coil 19 of the cathode 10 is heated by a conductor 5G leading from one terminal of a battery, as A, and by a conductor 57 which leads from the second terminal of the battery A. The potentiometer 54 is interposed in the conductors 5G, 57 as shown. A conductor 58 leads from the anode or plate 33 of the audion to the primary winding or coil 59 of an output transformer GO, and a conductor 61 leads from the Aprimary coil of this output transformer to the second ter minal of the battery B. The secondary winding or coil 62 of the output transformer GO may be connected to the incoming or primary winding of another radio circuit system or may be connected to a receiving instrument as occasion may require. The high frequency signals received by the antenna 45 are transmitted over conductor 44 through the primary coil 4G of the input transformer 47 and over conductor 48 to ground 49. The high frequency voltage induced in the secondary coil 50 of the transformer 47 is amplified by tuning the variable condenser 51. The

voltage transmitted in one direction from the secondary coil 50 will pass over conductors 53 to the cathode sleeve 24 of the cathode 10 through the heating coil 19 and its connection 23 to the cathode sleeve, through the potentiometer 54 which is in shunt with the conductors 56, 57 of the heating coil 19, this coil 19 being heated by the current from battery A passing thereto over conductors 56, 57.

The voltage alternations of the other terminal of the secondary coil 50 of the in ut transformer 47 will be conducted to the input electrode or grid 38 of the audion causing signal fluctuations in the stream of electrons or space current flowing from the cathode 10 to the anode or plate 33 of the output circuit which includes the conductor 58, primary windin or coil 59 of the output transfdrmer 61, conductor 61 leading from one terminal of the battery B and conductor 55 which leads from the second terminal of the battery B to potentiometer 54. The circuit is completed from the battery A, over conductors 56, 57 for heating the coil 19 from which the heat is transmitted to the cathode sleeve 24 through the tubular insulator 28 and causes from the cathode to emit an electron stream free from the electrical influence of voltage fluctuations from the heating coil.

The alternations of the space current in the output transformer 60 will induce alternating voltage in the secondary winding 62 of this output transformer which may be detected in this unit or further amplified as desired. The absence of voltage effects from the heating coil on the cathode sleeve overcomes to a large eXtent undesirable amplification of fluctuations in the heating current and makes it possible to heat the coil 19 with alternating current without diminishing the quality of the signal reception. Moreover, by connecting the heating coil 19 to the cathode sleeve 24 only the four terminals or pins 15, 16, 36, 41 are required and the necessity for usln; live terminal pins is avoided. This form o audion may therefore be used in standard radio systems.

In the foregomg description, I have embodied the preferred form of my invention, but I do not wish to be understood as limiting myself thereto as I am aware that modifications may be made therein without departing from the principle or sacrificin any of the advantages of this invention, t erefore, I reserve to myself the right to make such changes as fairly fall within the scope thereof.

I claim: Y

1. An electron discharge device comprising an envelope enclosing an anode and a cathode comprismg a metal ca sule open at one end and a hehcal bifilar ament with its two strands closely stplaced throughout their convolutions, said ament being mounted in- 65 side and coaxial of said capsule with its ode comprising a metal tube open at one end and with its wall bent to substantially close` the other end, a heater comprising a helical biilar filament mounted inside and coaxial of said tube with its middle point joined to the closed end of said tube, a pair of leads sealed into the walls of said envelope adjacent the open end of said tube and connected to the two adjacent ends of said filament to pass current thru the strands of said filament in series, and a support fixed to the wall of said envelope for maintaining said terminals and the open end of said tube insulated and spaced to hold said filament in position in said tube.

3. A cathode mount for electron discharge devices comprising a stem, a tubular insulator having one end fixed on said stem to project from said stem, a heater filament on said stern and within said insulator, and an electron emitting capsule with its open end fitted over said tubular insulator to support said capsule on said insulator.

4. A cathode mount for electron discharge devices comprising a stem having a pair of leads sealed into it, a tubular insulator fzlred on said stem to surround said leads, a reverse wound bifilar helical filament mounted inside said insulator with its ends connected to said leads, and a tubular metal sleeve tted over and supported by said insulator.

5. An electron discharge device comprising an envelope, a stem, a cylindrical insulating extension on the stem extending within the envelope, a tubular insulating member supported at one of its ends by the cylindrical extension, a heating element Within the tubular insulating member, leads extending through the cylindrical extension and electrically connected to the heating element, an electron discharge member supported on the outside of the insulating member, additional electrodes within the envelope, and leads extendin through portions of the stem other than t e cylindrical extension and connected to the' other electrodes.

This specification signed this 18th day of June, A. D. 1926.

WALTER J. ALBERSHEIM.

' .75 an envelope enclosing an anode and a cath' 

